Cast and assembly method for motor vehicle bodywork

ABSTRACT

A cast light metal joining element and method of assembly with adjoining extruded light metal hollow section bearer member of a space frame type vehicle body. The joining element or casting includes at least two spaced apart, location points disposed along a surface wall thereof. The location points permit the casting to be held in a corresponding fixture at a desired positionally correct spatial orientation to facilitate the fitting and connection of adjoining frame elements with greater ease, accuracy and smaller tolerances. In one embodiment, the location points include integrally formed conical studs and/or conical depressions. In another embodiment, the location points include through-holes, either straight cylindrical or conically tapered. The studs, depressions and/or holes also served a dual function in providing a positive locking connection to add on components which have corresponding matingly engagable connection surfaces.

FIELD

The present invention relates to improvements in motor vehicle bodyworkfabrication, and more particularly to an improved junction element in avehicle bodywork of the type having a space frame bearing structureassembled from a plurality of hollow section frame members joinedtogether by junction elements.

BACKGROUND

Customary self-supporting vehicle bodies for passenger vehicles,including the associated supporting structure, are manufactured fromsheet-metal parts. The bearer members which have hollow profiles areformed by welding together two deep-drawn metal sheets or stampings. Thebearer joints which form the connection of two bearers are typicallyformed by overlapping adjacent bearer ends and joining them at thepoints of contact with a weld seam or several spot welds.

The steel sheets used to construct such self-supporting vehiclebodyworks are typically shaped in a deep drawing process. While the diesused for shaping the steel sheets are relatively expensive, they doprovide a cost-favorable solution for mass production since they permitlarge production runs. However, in view of the high investment costs fortooling, the aforesaid process is very cost-intensive for smallerproduction runs.

A more cost-favorable solution for small production runs is known, forexample, from European Patent document EP 0 146 716. This documentdiscloses a "space frame" type bearing structure for a passenger carbody which comprises a plurality of hollow section frame members joinedtogether by nodes or junction elements. The hollow section frame membersare formed as extruded light-metal sections, typically high gradealuminum alloy, and the junction elements are formed as light-metalcastings. In addition to being a more cost-favorable solution for smallproduction runs, a light-alloy bodywork of the type disclosed in EP 0146 716 weighs less and offers improved corrosion resistance as compareto a conventional sheet metal bodywork.

Such cast light metal junction elements typically have very complexsurface configurations and include variable wall thicknesses, and/orreinforcing ribs for added stiffness as well as complex curved regionsfor making suitable transitions with even force distribution to theadjoining extruded hollow section frame members.

With such three-dimensionally complex structures, however, problemsarise in: (1) design; (2) the production of the patterns and molds; (3)checking or tolerance verification operations; and above all; (4) thefinal assembly of the finished joint. The above problems are due to thefact that there is no suitable and reproducible, geometrically simplebasic structure on the basis of which the design of, dimensioning,checking and adjustment or tweaking can be carried out.

For a body superstructure with narrow tolerances, it is difficult toarrange the complex-shaped junction elements in the correct position inspace and to assign the connecting extruded sections to them. This isdue to the unusually complicated geometry of the junction elements,which generally do not have any surfaces well suited for positionallycorrect mounting in an assembly device or jig. In addition, in view ofthe complex geometry, checking for dimensional accuracy of the parts ismade difficult, thus making it necessary to accept relatively largetolerances.

It is known from French Patent Document FR 556 458 A how to releasablyconnect two flat components on a vehicle by a central bolt, whereby themating surfaces of the two components have interengaging conical raisedportions and correspondingly shaped depressions. The describedengagement method provides an aid to adjustment and an anti-rotationsafeguard. No reference, however, is made to assembly of a vehicle bodyfrom junction elements and hollow sections.

A method for the production of a vehicle body is furthermore known fromGerman Patent Document DE 3 413 228 A1 in which the initial assembly ofthe vehicle body is completed without a center pillar and is fullypainted. In this way, interior fittings may be introduced into thepassenger compartment via the side cut-out where the center pillar wouldnormally be disposed. Once the interior fittings have been installed,the center pillar is then inserted and connected to the vehicle body.This connection is made via a conical plug-in connection. This document,however, does not teach or suggest a three dimensional positionallycorrect alignment of junction elements within an assembly device.

British Patent Document GB 941 164 discloses a substructure of a vehiclebody wherein a forwardly disposed transverse member is joined along eachend thereof via upwardly curved bridging members to a respective one ofa pair of parallel, spaced apart longitudinal frame members. Thetransverse member and the longitudinal members lie in parallelhorizontal planes. The mating surfaces between the ends of thetransverse member and the curved bridging members include upraisedbosses and corresponding recesses to facilitate releasable engagementand orientation of the curved bridging member for final connection withthe associated longitudinal member. This document does not teach orsuggest a method for fixing a junction element in space to assist in theassembly of a plurality of adjoining frame elements thereto.

THE INVENTION Objects

It is therefore an object of the invention to provide a method forassembly of a vehicle body having a space frame type bearing structurewhich comprises hollow section members interconnected by junctionelements which is simple to carry out and results in dimensionallyaccurate vehicle bodies.

It is another object of the invention to provide a joining element inthe form of a cast component which includes a plurality surfaceconfigurations formed thereon which serve as datum points for fixing thecast component in an assembly device or jig in a desired spatialorientation for positionally correct connection of adjoining frameelements with small tolerances.

Other and further objects will become evident from the following writtendescription, drawings and appended claims.

DRAWINGS

An exemplary embodiment of the invention with further details, featuresand advantages is best understood with reference to the drawings inwhich:

FIG. 1 shows an isometric view of a cast component in the form of asuspension strut mount.

SUMMARY

According to the invention, the joining elements are in the form oflight metal castings and have at least two spaced apart, master pointsin the form of integrally formed raised portions and/or integrallyformed depressions provided on a wall surface thereof. The castings areheld in the correct position in space by way of the master points byclamping into a measurement fixture or holding in an assembly device orjig during assembly. Extruded section frame members are then joined tothe castings by welding or adhesive bonding.

Dependent upon these master points, the dimensioning is accomplished,whereby the master points represent appropriate datum points. At thesame time, through their shape as integrally formed raised portionsand/or integrally formed depressions, registration is possible, forexample, for clamping into a measurement fixture or for holding duringassembly.

The master points advantageously aid in the construction of the modelfor the cast component, since the model, beginning from the masterpoints, is set in its shape and thus, despite complex contours, issimple to manufacture. Similarly, the manufacture of the casting toolsis simplified, whereby the measurement of the casting tools, beginningfrom the master points, can be well controlled.

Also, once the master points have been entered into the measurementfixture, the finished castings can be simply measured and controlled,even in the case of very irregular shapes.

Further, in the case of bodywork repair, it is possible to use themaster points to measure with relative ease the bodywork joint elements.

The master points of the present invention thus result in substantialadvantages for model construction, tool construction, and in control andmeasurement work. The master points can, however, also advantageouslyassist the assembly, whereby such a casting is held in the correctposition in space by way of the master points until finally joined tothe extruded sections by welding or adhesive bonding.

In another advantageous embodiment of the present invention's castcomponents, the master points, when configured as raised portions ordepressions, may be used to facilitate positive engagement withadditional add-on parts having corresponding engaging surfaces. Thisresults in positively engaged force transmissions, whereby tensionalpeaks can be reduced by a homogeneous introduction of force. In suchpositively engaged junctions, respectively concave or convex formedparts interlock in the region of the master points.

In another embodiment of the invention, three assigned master pointsdefining a triangular area are provided. The three master points definean area on the cast component from which all the relative arrangementsrequired for correct positioning in space are possible. In the case of amulti-surface cast component, such a triangular area, defined by masterpoints, is expediently also placed in this plane. In the case ofcastings of complex design, however, further master points may also beexpedient.

In a particularly preferred embodiment, the master points are designedas conical studs. With such studs, a cast component can be fixed andcentered in a simple manner in an assembly device. Force transmissionwith positive engagement can also be carried out in a simple manner byvirtue of such studs since the force-transmitting surfaces come intoplay-free contact due to the conical structure. Ease of removal from themold is likewise guaranteed.

The cone axes of the conical studs preferably all point in the samedirection in space in accordance with the direction of attachment. Inthis way, the casting can be held in a corresponding assembly device ina simple manner.

In one embodiment of the invention, the master points, embodied asintegrally formed depressions, are cylindrical holes. These holes canalso penetrate the casting wall, thereby allowing them to serve theadditional function of receiving screw fasteners.

In another embodiment of the invention, the depressions are designed asconically tapered holes similar to the conical studs, being the negativeform of the latter. Here, too, this gives the corresponding advantagesfor fixing and centering and force transmission with positive engagementif the counterparts are of correspondingly conical design.

As with the embodiment of the master points as conical studs, it isadvantageous to align the central longitudinal axes of the holes in thesame direction in space to ensure that the parts can be fitted togethereasily.

The master points are preferably provided on suitably stiff and strongregions of the casting. For this purpose the casting may be selectivelyreinforced by added wall thickness and/or supporting ribs. Thisguarantees good dimensional stability of the master points relative toone another.

DETAILED DESCRIPTION OF THE BEST MODE

The following detailed description illustrates the invention by way ofexample, not by way of limitation of the principles of the invention.This description will clearly enable one skilled in the art to make anduse the invention, and describes several embodiments, adaptations,variations, alternatives and uses of the invention, including what wepresently believe is the best mode of carrying out the invention.

FIG. 1 shows a casting or cast component 1 embodied as a frontsuspension strut mount. This cast component 1 is representative of onetype of junction element of the supporting structure of a vehicle body.The casting preferably comprises a light-metal alloy. In the presentexample, the casting 1 includes three lateral shoulders 3, 4, 5 to whichaluminum extruded sections (not shown) are connected to construct thesupporting structure. The central portion 5 is arched somewhat upwardsin a cup shape and serves as a support and attachment for a suspensionstrut (not shown) which is placed against it from below after finalassembly.

As is evident from FIG. 1, the casting 1 when embodied as a suspensionstrut mount is of relatively irregular and complex design in order tosatisfy the requirements for attachment of the adjoining light-metalextruded sections, including the desired stiffness characteristic andsmooth force transmission for the resulting joint.

Two spaced-apart conical studs 6 and 7 are provided in a upper surfaceas master points. The conical studs 6 and 7 include cone axes 8 and 9,respectively, which preferably are aligned in parallel, approximatelyvertical axes.

The studs 6 and 7 represent datum points by which adjustment andorientation in a desired spatial position may be accomplished by fixturein a suitable assembly device such as, for example, clamping the datumpoints to corresponding receiving conical depressions of a provided jig.Once the casting 7 is fastened at the master points in the desiredspatial orientation, it is a simple matter to verify the tolerances andrelated measuring/checking procedures.

In an alternate embodiment, the datum points may comprise a plurality ofintegrally formed depressions or holes. FIG. 1 shows three holes 10, 11,12, approximately defining a triangular area, on the casting. The holes10, 11 and 12, also have central longitudinal axes, indicated by theirrespective reference numerals 10a, 11a and 12a, all of which preferablypoint in the same direction in space. These holes 10, 11, 12 are alsopreferably formed integral within the casting 7 from the outset andrepresent master points. The holes 10-12 may be either cylindrical orconically tapered as desired.

In both embodiments, the studs 6, 7 and the holes 10, 11, 12 arepreferably situated in thick-walled or ribbed reinforced regions of thecasting 1.

As an be seen, without the studs 6, 7 and/or the holes 10, 11, 12, theirregular shape of the casting 1 would make it difficult to adjust andfix the casting 1 in space, for example to connect the light-metalextruded sections. In yet another embodiment the three holes can bereplaced by three or more conical studs.

In the present case, the holes 10, 11, 12, embodied as master points,can simultaneously also be used as seats for the screwed fasteners bymeans of which the suspension strut is fastened. Further connectingparts can also be positioned over and screwed down on the studs 6 and 7with positive engagement and in a centered manner described abovethereby providing good force transmission with positive engagement andreduced stress peaks in addition to the screwed-in components.

It should be understood that various modifications within the scope ofthis invention can be made by one of ordinary skill in the art withoutdepartment from the spirit thereof. For example, while the datum pointshave been described as consisting of either all studs or all holes, itis understood that a combination of studs and holes may be used asdesired. We therefore wish our invention to be defined by the scope ofthe appended claims as broadly as the prior art will permit, and in viewof the specification if need be.

PARTS LIST

1. Suspension strut mount

2. Shoulder

3. Shoulder

4. Shoulder

5. Central portion

6. Conical stud

7. Conical stud

8. Core axis

9. Core axis

10. Hole

11. Hole

12. Hole

We claim:
 1. A method of assembly of a vehicle bodywork having a spaceframe bearing structure of the type in which cast light metal junctionelements are used to join a plurality of extruded light metal hollowsection frame members, said assembly method comprising the steps of:a)providing a cast light metal junction element having a plurality ofconnector portions for joining a plurality of converging extruded lightmetal hollow section frame members and including at least one wallsurface having a plurality of spaced apart datum points thereon; b)clamping said cast light metal junction element to a fixture at saiddatum points so that said cast light metal junction element is held at adesired spatial orientation; c) securing each of said plurality of saidextruded light metal hollow section frame members to their correspondingconnector portions of said cast light metal junction element; and d)unclamping said cast light metal junction element from said fixture. 2.A vehicle bodywork assembly method as in claim 1 wherein said datumpoints comprise three master points disposed in triangular orientationon said cast light metal junction element.
 3. A vehicle bodyworkassembly method as in claim 2 wherein said master points compriseupraised conical studs.
 4. A vehicle bodywork assembly method as inclaim 3 wherein:a) said cast light metal junction element includesreinforced wall thickness regions to provide for improved stiffness; andb) said reinforced wall thickness regions are disposed adjacent saidconical studs.
 5. A vehicle bodywork assembly method as in claim 3wherein:a) each of said conical studs has a central longitudinal axis;and b) said central longitudinal axes of said conical studs are parallelto one another.
 6. A vehicle bodywork assembly method as in claim 5wherein:a) said cast light metal junction element includes reinforcedwall thickness regions to provide for improved stiffness; and b) saidreinforced wall thickness regions are disposed adjacent said conicalstuds.
 7. A vehicle bodywork assembly method as in claim 2 wherein saidmaster points comprise cylindrical holes.
 8. A vehicle bodywork assemblymethod as in claim 7 wherein:a) said cast light metal junction elementincludes reinforced wall thickness regions to provide for improvedstiffness; and b) said reinforced wall thickness regions are disposedadjacent said cylindrical holes.
 9. A vehicle bodywork assembly methodas in claim 7 wherein:a) each of said cylindrical holes has a centrallongitudinal axis; and b) said longitudinal axes of said cylindricalholes are parallel to one another.
 10. A vehicle bodywork assemblymethod as in claim 9 wherein:a) said cast light metal junction elementincludes reinforced wall thickness regions to provide for improvedstiffness; and b) said reinforced wall thickness regions are disposedadjacent said cylindrical holes.
 11. A vehicle bodywork assembly methodas in claim 2 wherein said master points comprise conically taperedholes.
 12. A vehicle bodywork assembly method as in claim 11 wherein:a)said cast light metal junction element includes reinforced wallthickness regions to provide for improved stiffness; and b) saidreinforced wall thickness regions are disposed adjacent said conicallytapered holes.
 13. A vehicle bodywork assembly method as in claim 11wherein:a) each of said conically tapered holes has a centrallongitudinal axis; and b) said central longitudinal axes of saidconically tapered holes are parallel to one another.
 14. A vehiclebodywork assembly method as in claim 13 wherein:a) said cast light metaljunction element includes reinforced wall thickness regions to providefor improved stiffness; and b) said reinforced wall thickness regionsare disposed adjacent said conically tapered holes.
 15. A vehiclebodywork assembly method as in claim 1 wherein said datum pointscomprise upraised conical studs.
 16. A vehicle bodywork assembly methodas in claim 15 wherein:a) said cast light metal junction elementincludes reinforced wall thickness regions to provide for improvedstiffness; and b) said reinforced wall thickness regions are disposedadjacent said conical studs.
 17. A vehicle bodywork assembly method asin claim 15 wherein:a) each of said conical studs has a centrallongitudinal axis; and b) said central longitudinal axes of said conicalstuds are parallel to one another.
 18. A vehicle bodywork assemblymethod as in claim 17 wherein:a) said cast light metal junction elementincludes reinforced wall thickness regions to provide for improvedstiffness; and b) said reinforced wall thickness regions are disposedadjacent said conical studs.